FURTHER OBSERVATIONS ON THE TRANSMISSION AND DEVELOPMENT OF LEUCOCYTOZOON SIMONDI

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Abstract
Observations are presented on the incidence of Leucocytozoon simondi in ducklings during several summer seasons. Species of black flies of the subgenus Eusimulium (Simulium croxtoni and Simulium euryadminiculum) and Simulium rugglesi feed on ducks and have been shown to be suitable hosts for L. simondi. The former species appear to be the important vectors of the parasite in the early part of the black fly season and the latter species in late June and July. Development of the parasite in S. rugglesi has been followed. Oöcysts occur in, and on, the stomach wall, and sporozoites are found in the salivary glands. The small oöcysts contain relatively few sporozoites. The data suggest, but do not prove conclusively, that sporogony, although variable, can be completed in three or four days. Specimens of S. rugglesi contained viable sporozoites 18 days after the flies had their final blood meal containing gametocytes. The splenomegaly, changes in the composition of the blood, size of parasites, and presence of asexual stages in the tissues, were observed in infected ducks in relation to the time of infection and as a result an hypothesis is presented regarding the asexual cycle.